Fluidic speed governor

ABSTRACT

A fluidic speed governor for controlling the speed of pneumatic or hydraulic machines senses the machine speed directly from pressure pulsations in the pressurized fluid supply or exhaust of the machine. The governor includes a fluidic speed-sensing circuit having no moving mechanical parts and an input connected to the pressurized fluid supply or exhaust of the machine for generating a DC-type pressurized fluid signal having a pressure magnitude proportional to the pressure pulsation frequency which is directly proportional to the actual machine speed. A second fluidic circuit connected to the output of the first circuit is provided with a speed reference input signal and generates a pressurized fluid signal indicative of the deviation of the actual machine speed from the reference speed. A fluid power amplifier connected to the output of the second circuit develops a pressurized fluid flow for controllably driving the governed machine.

United States Patent [50] Field of Search Inventor Martin C. Doherty Scotia, N.Y. Appl. No. 808,869 Filed Mar. 20, 1969 Patented May 25, 1971 Assignee General Electric Company FLUlDlC SPEED GOVERNOR 7 Claims, 7 Drawing Figs.

US. Cl

Int. Cl

[56] References Cited UNITED STATES PATENTS 2,879,467 3/ 1 959 Stern 3,059,480 10/1962 Carpenter 3,195,525 7/1965 Beck 3,400,729 9/1968 Boothe 3,409,032 1 1/1968 Boothe et al Primary Examiner-James J. Gill AttorneysPaul A. Frank lohn F. Ahern, Louis A. Moucha,

Frank l... Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: A fluidic speed governor for controlling the speed of pneumatic or hydraulic machines senses the machine speed directly from pressure pulsations in the pressurized fluid supply or exhaust of the machine. The governor includes a fluidic speed-sensing circuit having no moving mechanical parts and an input connected to the pressurized fluid supply or exhaust of the machine for generating a DC-type pressurized fluid signal having a pressure magnitude proportional to the pressure pulsation frequency which is directly proportional to the actual machine speed. A second fluidic circuit connected to the output of the first circuit is provided with a speed reference input signal and generates a pressurized fluid signal indicative of the deviau'on of the actual machine speed from the reference speed. A fluid power amplifier connected to the output of the second circuit develops a pressurized fluid flow for controllably driving the governed machine.

PATENIEU "M25197! 3; 580,086

sum 3 or 3 in van t or: Martin C. Dohery FLUIDIC SPEED GOVERNOR My invention relates to a fluidic device for controlling the speed of pneumatic or hydraulic machines by sensing the speed directly from pressure pulsations in the pressurized fluid supply or exhaust of the machine, and in particular, to a fluidic speedsensing circuit having an input connected to the pres surized fluid supply or exhaust of the machine and having no moving mechanical parts.

Many types of pneumatic and hydraulic machines of the positive displacement type, such as air motors, which operate with pressurized fluid are generally very load sensitive in that the machine speed varies substantially as the load on the machine is changed. A speed governor is thus required in many applications such as industrial hand tools and dental drills to maintain a relatively constant speed with load change.

Prior art fluid, mechanical and electronic speed governors utilize conventional separate shaft speed sensors such as the ballhead or chopper wheel, having mechanical moving parts. The moving parts feature of the speed sensor has the obvious disadvantage of being subject to wear and, or, eventual failure as well as occupying substantial space which may be at a premium in the particular application. Thus, there is a need for a speed governor which utilizes a rotational speed sensor having no moving mechanical parts.

Therefore, one of the principal objects of my invention is to provide a speed governor having a speed sensor component utilizing no moving mechanical parts.

Another object of my invention is to sense the pressure pulsations generated in the pressurized fluid supply or exhaust of the governed machine as a measure of the actual machine.

A further object of my invention is to provide fluidic circuitry for converting the pressure pulsations to an analog type pressurized flow signal for controllably driving the governed machine.

Briefly stated, and in accordance with the objects of my invention,'I provide a fluidic speed governor having a speedsensing component comprised of no moving mechanical parts. The governor includes a first fluidic circuit functioning as a fluidic tachometer, a second fluidic circuit for generating a speed-correcting signal, and a fluid power amplifier for developing sufficient fluid flow to controllably drive the governed pneumatic or hydraulic machine. The input to the first fluid circuit is connected to the pressurized fluid supply, housing or exhaust of the governed machine for sensing pres sure pulsations therein generated by rotation or reciprocation of moving parts in the machine. The pressure pulsation frequency is directly proportional to the actual machine speed. The second fluidic circuit is connected to the output of the first circuit and is provided with a speed reference input signal and develops at the output a pressurized fluid signal indicative of the deviation of the actual machine speed from the reference speed.

The features of my invention which I desire to protect herein are pointed out with particularity in the appended claims.

The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like parts in each of the several FIGS. are identified by the same reference character, and wherein:

FIG. 1 is a schematic diagram representation of a fluidic speed governor constructed in accordance with my invention;

FIG. la is a block diagram of the governor;

FIG. 2 is a series of waveforms of fluid signals in various parts of the governor circuit;

FIG. 3 illustrates an input connection for sensing the pressure pulsations in the exhaust, housing or fluid supply of the governed machine;

FIG. 4 is a schematic diagram of a second embodiment of the decoupling circuit and input stage of the governor tachometer circuit; and

FIGS. 5a and 5b are schematic diagrams of twoadditional embodiments of the frequency-to-analog converter stage of the tachometer circuit.

Referring now in particular to the schematic diagram of FIG. 1, my fluidic governor is comprised of three components, a fluidic tachometer 10, a multistage fluidic amplifier 11 and a fluid power amplifier 12. The block diagram of FIG. la indicates the overall functional relationships of the various components in a speed governor system wherein power amplifier l2 varies the pressure of, and thereby controllably supplies, the pressurized fluid to the governed machine. Tachometer I0 is provided with an input for sensing pressure pulsations in the housing, pressurized fluid supply or exhaust 13 of the governed machine (a positive displacement-type pneumatic or hydraulic machine), a fluidic decoupling circuit 14, multistages of proportional-type fluid amplifiers 15, two stages of digital-type fluid amplifiers 16 and a fluidic frequency-toanalog converter circuit 17. The input to tachometer 10 comprises one of the most important features of my invention and will now be described in some detail with respect to FIGS. 1, 2 and 3.

The positive displacement-type pneumatic and hydraulic machines which my fluidic speed governor is especially well adapted for controlling the speed thereof, have the characteristic of generating pressure pulsations in the housing, pressurized fluid supply and exhaust of the machine due to the reaction of the motion of sliding vanes, rotors, pistons or gear teeth on the fluid passing through the machine. These machine-generated pressure pulsations have a wave shape and repetition rate determined by the geometry of the machine elements, and the wave shape is generally somewhere between a square wave and sine wave of relatively small amplitude compared to the steady state (DC) pressure level of fluid in the machine supply or exhaust. The pulsation peak-to-peak amplitude may be in the order of 0.1 pounds per square inch (p.s.i.), is generally somewhat variable, and the DC level is from 0.1 to 5.0 p.s.i. in the machine exhaust as illustrated in FIG. 2A. The'capital letter designation for each waveform in FIG. 2 identifies the corresponding lettered location of such waveform in FIG. 1. In the case of sensing pulsations in the machine fluid supply, the DC level is much greater and in the order of at least 5 p.s.i., all of the single-sided pressures being in terms of p.s.i. gauge. The fluid employed in my governor is a gas such as air in the case of pneumatic machine applications, and a liquid such as oil in the case of hydraulic machine applications.

As illustrated'in FIG. 3, the input to the fluidic tachometer 10 may comprise a T-connection 30 or other suitable fitting in the housing or fluid line 13 of the governed machine. This T- connection may be located anywhere in the fluid supply or exhaust line, (i.e., between the governed machine housing and the pressurized fluid output of power amplifier 12 or exhaust). The T-fitting 30 may be fabricated of any suitable material which is appropriate to the particular application, such as a metal, plastic, and the like. The pickoff point may even be at the exhaust muffler 31, it being understood that the latter location is especially suitable for larger machines wherein the pressure pulsations are generally of greater amplitude such that the muffler action will not wash out such pulsations. In the latter case, the pickoff may comprise a threaded fitting 32 which merely provides an opening in the sidewall of the muffler adjacent the downstream end thereof. The tubing 33 connecting pickofi' 30 or 32 to the input of tachometer 10 may be fabricated of any suitable flexible or nonflexible material such as plastic, copper and the like, the particular material being determined by the specific application. The diameter of tubing 33 is determined primarily by the fluidic circuitry to which the other end of the tubing is connected. In general, tubing 33 is of inner diameter in the range of one-tenth inch to one-fourth inch.

Referring now to FIG. 1, and assuming fluid line 13 is the machine exhaust line, it may be considered to have an effective small fluid flow resistance 13a and the muffler is indicated as a more general vent means 31. The second end of interconnecting tubing 33 is connected to the input of fluidic tachometer circuit which is similar to the circuit described in U.S. Pat. No. 3,409,032 to Boothe et al. and assigned to the assignee of the present invention. The subject patent, however, utilizes a moving parts speed sensor coupled to the rotating shaft of a machine as opposed to applicant's no moving mechanical parts sensor. The decoupling circuit 14 is the control input circuit to a first stage proportional type fluid amplifier 15a, and consists of a first fluid flow restrictor R in a first control fluid inlet of the amplifier, and a second restrictor R and fluidic capacitor C, in the second and opposed control fluid inlet. The two restrictors R,, R are of equal dimension to provide equal resistances to fluid flow therethrough. Capacitor C, may bea fixed volume for pneumatic applications or a hydraulic accumulator for hydraulic applications. The decoupling circuit 14 is described in detail in U.S. Pat. No. 3,400,729 to Boothe and assigned to the assignee of the present invention. Briefly, the R C resistance-capacitance circuit (or a resistance-inductance circuit) in the second control fluid inlet delays the response in such control inlet to transient fluid pressure signals such as the pressure pulsation signal A illustrated in FIG. 2A passing through tubing 33 to amplifier 15a. The time constant T of the R-C (or R-L) circuit in the second control fluid inlet is sufficiently large such that the corresponding frequency HT is approximately one-tenth of the lowest frequency in the normal operating frequency range of the speed governor. Thus, with reference to the attenuation versus frequency characteristics FIG. 3 of the Boothe U.S. Pat. No. 3,400,729, the R C values are chosen such that the break frequency separating frequency ranges A and B is at a sufficiently low frequency whereby the decoupling circuit 14 operates in the higher frequency range B wherein any change in the signal pressure amplitude at the output of proportional amplifier 15a is solely dependent on amplitude changes in the pressure pulsation signal A sensed in the governed machine exhaust line 13. Fluidic circuit 14 thus operates as a decoupling circuit, slightly attenuating the AC component (the pressure pulsations) of the input signal, and converting the single-sided input signal into a push-pull or differential pressurized signal of the same frequency. The normal operating frequency range of my governor for many applications is approximately 100 to 1,500 Hertz, and thus the values of R C are chosen to obtain a break frequency of approximately 60 Hertz and a corresponding time constant T=R C of approximately 0.003 seconds.

The output of the first stage proportional amplifier 15a is supplied to the control fluid inlets of a second stage proportional amplifier 15b, and the outputs thereof to a third stage 15c. Proportional amplifiers 15a, 15b, 150 are of conventional type and provide a total open loop forward gain of approximately 30. The amplifiers are generally operated in their linear range of operation, although the circuit is also satisfactorily operable upon the saturation of one or more of these amplifiers. Due to the relatively high gain of the three-stage amplifier 15, the DC pressure levels in the two fluid receivers of the third stage amplifier 150 may be different due to slight manufacturing imperfections in any of the three stages which tend to develop a slight bias pressure. To assure equal DC pressure levels in the two receivers of third stage amplifier 150, one, or possibly two pairs of negative feedback passages are provided in the amplifier circuit. The negative feedback paths are from the receivers of the third stage amplifier 15c to the control fluid inlets of the first stage 150, and possibly also to the third stage. A fluid flow restrictor is provided in each of the negative feedback passages as indicated by resistors R in the feedback loop around the three amplifiers, and resistors R in the feedback around only the third amplifier. The resistors R are generally of substantially equal resistance value and the resistors R are also of equal value. If both pairs of feedback passages are employed, the resistance of resistor R is much greater than the resistance of resistor R and the resistance of resistor R is approximately 100 times the resistance of R or R Typical waveforms and pressure values of the pressure signals at the output of third stage amplifier 15c are indicated in FIGS. 2C1 and 2C2 and the corresponding C1, C2 locations are indicated in FIG. 1. It should be obvious that the multistages of proportional amplifiers 15 may include a plurality of serially connected amplifiers of number less or greater than the indicated three as determined by the desired gain. In the case of an odd number of amplifiers, the feedback circuitry and waveforms C1 and C2 would be similar, however, in the case of even number of fluid amplifier stages, the

feedback loops around the several amplifiers would be connected to the opposite control fluid inlets of the first stage and the FIG. 2C and 2C2 waveforms would be interchanged. ,The particular shapes of the Cl and C2 waveforms depends upon the shapes of the input pressure pulsations and the operating characteristics of the several fluid amplifiers in multistage circuit l5 and whether such amplifier operation is in the linear or saturated range.

The fluidic frequency-to-analog converter circuit 17 utilizes a digital (substantially square wave) type pressurized fluid input signal. Since the output of the proportional amplifier stages 15 may be of wave shape between a sine wave and square wave, two stages of digital type fluid amplifiers 16 are connected between the output of circuit 15 and the frequency-to-analog converter circuit 17 to assure a square wave input thereto. Digital amplifiers 16 may thus be considered the input stage of converter circuit 17. Thus, the Cl and C2 outputs of the third stage proportional amplifier are connected to the control fluid inlets of a first stage digital amplifier 16a and the outputs thereof to a second stage digital amplifier 16b. These fluid amplifiers, as well as all of the others herein described, are of conventional design utilizing a power fluid inlet, two opposed control fluid inlets and one or two receivers as illustrated in FIG. 1. The square wave output of the second stage 16b is illustrated in FIGS. 2D] and 2D2, and the relative amplitude of the square wave and DC level magnitude for a typical application are indicated. The repetition rate of the square wave pulses is equal to the repetition rate or frequency of the input pressure pulsations.

The frequency-to-analog converter circuit 17 further includes a single-receiver proportional-type fluid amplifier device commonly designated as a fluidic full-wave rectifier wherein the receiver is aligned with the power nozzle. F luidic capacitors C are provided in the opposed control inlet passages of rectifier 17a which are connected to the receivers of digital amplifier 16b. Converter circuit 17 has the charac teristic, as explained in detail in the aforementioned Boothe et al. U.S. Pat. No. 3,409,032, for developing a pulsating output signal wherein the DC pressure level is directly proportional to the magnitude of the input frequency signal, that is, the pressure pulsations in exhaust line 13. The frequency operating range of circuit 17 is approximately 100 to 1,500 Hertz. The waveform at the output of rectifier 17a is indicated in FIG. 2B wherein the pulsating amplitude is generally less than 0.1 p.s.i. and the magnitude of the DC pressure level is directly proportional to actual machine speed. The tachometer circuit 10 gain is determined from this DC pressure level, knowing the actual machine speed, and in typical example may be in the order of 2.0 p.s.i./ 1,000 Hz. wherein the frequency of 1,000 Hertz represents an air motor speed of (l,O00 60)/4 rpm. for a four vane machine. All of the waveforms are in terms of pressure in p.s.i. gauge vs. time, and the decreasing magnitude of DC pressure in the FIG. 2E waveform indicates a decrease in machine speed (from the desired or reference value) such as occurs due to increased machine load. This decrease in machine speed is also indicated in the previous waveforms of FIG. 2 by the decreasing frequency of the individual pressure signals. The pulsating portion of the signal at the output of rectifier 17a is filtered by capacitor C, connected to the output of the receiver of rectifier 17a to provide a substantially steady state or DC pressure level tachometer output signal. The filtered output of the frequency-to-analog converter circuit has substantially linear characteristics over the normal operating range thereof. The fluidic tachometer circuit thus generates a single-sided DC pressure signal having a pressure magnitude varying linearly with, and directly proportional to, the frequency of pressure pulsations in the fluid supply or exhaust 13 of the governed machine, which in turn is directly proportional to the actual machine speed.

The tachometer output signal is applied to a first control inlet of a first stage amplifier 11a in the multistage proportional fluidic amplifier circuit 11. The second and opposite control inlet of the first stage 11a is supplied with a reference control fluid signal which establishes the desired speed setting for the governed machine. The reference pressure corresponding to the desired speed setting is obtained from a fluid bridge circuit including valves 18 and 19 serially connected across the system pressurized fluid supply P,. Supply P, also provides the pressurized power fluid directly to power amplifier 12, and through one or more resistors 21 to the various power fluid inputs in the governor circuits 10, 11 as indicated in FlG la. Source P, provides fluid at a relatively constant pressure which may vary as much as :10 percent. Valves 18, 19 may comprise any suitable pressure valves, valve 18 being of the fixed or variable type whereas valve 19 is of the variable type and in many applications is the speed setting valve, such as a variable relief valve operated by a foot pedal by the dentist in the case of a dental drill air motor application. The reference pressure signal is obtained from the juncture of valves 18 and 19 and is supplied to a second and opposed control fluid inlet of first stage amplifier 11a in the multistage fluid amplifier circuit 11. The power fluid is continuously supplied to amplifier 11a (and all the other fluidic devices in the governor) during the operation of the governor. When the governed machine is at the desired (reference) speed, there is a slight differential output signal across the two receivers of amplifier 11a of pressure magnitude directly proportional to the desired speed. In the case wherein the governed machine is operating at other than the desired speed, a change in the differential output of amplifier 11a is proportional to the deviation (error) of the actual machine speed from the desired speed as set by valve 19.

The waveforms at the output of first stage amplifier 11a are illustrated in FIGS. 2F1 and 2F2 wherein the pressure level of F1 is slightly greater than F2 (in the order of tenths of a psi.) for an odd number of amplifier stages in circuit 11 during a first interval wherein the actual machine speed is equal to the reference speed. This pressure level may typically be in the order of2 p.s.i. for a machine speed of 15,000 rpm. During a second interval wherein the machine speed has decreased as due to an increased load on the governed machine, the pressure of F 1 increases and F2 decreases, the change in the differential output between F1 and F2 being proportional to the speed error. The Fl-F2 signal is further amplified in second and third amplifier stages 11b and 11c. A single-sided output of the third stage amplifier 11c is utilized as the input to power fluid amplifier 12, and the second output is suitably vented. This single-sided amplified signal at the output of third stage amplifier 11c is a speed correcting signal and is indicated in FIG. 2G wherein the reference speed pressure level is in the order of l to 2 p.s.i. The signal of FIG. 26 is thus of pressure magnitude directly proportional to the algebraic sum of the reference speed and speed correction required for controlling the machine speed. The various DC and AC amplitude values noted herein are, of course, dependent upon the gains of the various fluid amplifier circuits and may be varied for a particular application.

The power amplifier 12 may be any suitable type which provides the necessary fluid flow amplification for controllably supplying pressurized fluid to, and thereby controllably driving, the governed machine. As one example, power amplifier 12 may be a pilot actuated relay valve which develops a speedcorrecting pressurized fluid flow sufl'rcient to drive the governed machine toward the reference speed and control the speed within limits set by the gain of the governor. Thus, component 12 is the only element in my governor which may have a moving mechanical part during operation at one reference speed setting.

FIG. 4 illustrates a second embodiment of the fluidic decoupling circuit 14 at the input of tachometer 10. In particular, the decoupling circuit again comprises a pure resistive element R in a first control fluid inlet of proportional amplifier 150, but in the second control inlet the circuit comprises a series connected resistive element R and an inductive element L wherein the inductor is a long tube of small diameter to obtain an L-R time delay circuit. This decoupling circuit obtains the same function as the decoupling circuit illustrated in FIG. land is also described in the aforementioned US. Pat. No. 3,400,729.

FIG. 5a is a second embodiment of the frequency-to-analog converter circuit 17 utilized in tachometer circuit 10 of my speed governor. This circuit is described in the aforementioned US. Pat. No. 3,409,032 and includes a fluidic resistance-capacitance network R C in a first control fluid inlet of rectifier 17a and a purely resistive element R in a second and opposed control inlet of the rectifier. The R-C network and purely resistive element are both connected to a first output of digital amplifier 16b and the second output thereof is vented. The filtered output of rectifier 17a provides an output signal inversely proportional to the input frequency and therefore the control fluid inlets to proportional amplifier lla must be interchanged to obtain the same speed control action as described with reference to the circuit of FIG. 1.

FIG. 5b illustrated a third embodiment of a frequency-toanalog converter circuit 17 which is described in full detail in copending Pat. application Ser. No. 686,602 to Carl W. Woodson, filed Nov. 29, 1967 and assigned to the assignee of the present invention. The frequency-to-analog conversion is obtained by the use of an inductive element L connected across the outputs of digital amplifier 16b (and the control inputs of rectifier 17a), and alternatively, such fluidic inductor may have a vented center tap as indicated by the dashed lines. The output signal characteristics of the FIG. 5b converter circuit are similar to those of 5a in that the pressure magnitude of the filtered output signal is inversely proportional to the frequency of the input signal.

My fluidic speed governor operates satisfactorily over an input pulsation frequency range of approximately to 1,500 Hertz and such range may be extended to approximately 3,000 Hertz by utilizing miniature size fluid amplifier devices (power nozzle diameters of approximately 0.010 inch). The operating characteristics of the speed governor depend primarily on the gain of the speed governor component circuits and thus depend upon the number of proportional amplifiers utilized in stages 15 and 11, and the gain of power amplifier 12. In one typical example, a total gain of 1 p.s.i./60 r.p.m. from the input of decoupling circuit 14 to the output of power amplifier 12 was realized to produce a closed loop operating characteristic wherein the actual machine speed decreased 15 percent from rated speed when going from no load to rated load. In open loop operation (absence of. the speed governor) the machine stalled for the same load change.

My fluidic speed governor hereinabove described operates with a relatively clean fluid in the pressurized fluid supply or exhaust line 13 of the governed machine. In some cases this fluid becomes contaminated by oil and the like within the machine housing wherein the pressure pulsations are generated, and this contamination, if passed into decoupling circuit 14 and fluid amplifier 15a could cause contamination and improper operation of the speed governor. The contaminated fluid is prevented from enteringthe decoupling circuit 14 by means of an optional isolation circuit 20. Circuit 20 consists of a source of clean, relatively constant pressurized fluid P which is connected through fluidic resistor R, to the tubing 33, preferably at some point B at, or just prior to the juncture of resistors R, and R, Source P in most instances would be the system source P after being suitably reduced in pressure level. Tubing 20a. connects the isolation circuit to tubing 33 and forms a If-DCIWOI'k with the exhaust line 13 and tubing 33. Tubing 20a connects a first end of resistor R to supply P and a second end to tubing 33. The pressure of the fluid at supply P must be greater than the DC pressure level of the fluid in line 13 such that it reverses the flow of fluid through the tubing 33 portion of -the IT-CIWOI'k while permitting the pulsating pressure (AC) portion of the exhaust fluid to pass through to decoupling circuit 14. For the example wherein the DC pressure level of the exhaust fluid (at A) is approximately 0.4 p.s.i., the pressure of supply l is approximately L8, and the resistance values of resistors R and R are approximately 1,000 and 2,000 seconds/inch, respectively, such that the pressure at the juncture (B) of resistor R and tubing 33 is approximately 1.5 p.s.i., see waveform of FIG. 2B. In general, the resistance of R a is approximately one-half of R,. Thus, the supply pressure I, and resistor R, are chosen to have reverse flow through tubing 33 at the worst conditions of the governed machine operation (the highest DC pressure level of fluid in exhaust line 13). In like manner, the isolation circuit may be utilized when sensing pressure pulsations in the housing or input supply line of the machine, in which case the pressure of supply I, would be at a suitably higher value to assure the reverse flow through tubing 33. Isolation circuit 20 is described and claimed in applicants concurrently filed US. Pat. No. application Ser. No. (RD-2967) entitled Fluidic Input Isolation Circuit," and assigned to the assignee of the present invention.

From the foregoing description, it can be appreciated that my invention makes available a new fluidic speed governor which is adapted for controllingthe speed of pneumatic or hydraulic machines by sensing the machine speed directly from pressure pulsations in the housing, fluid supply or exhaust of the machine. The speed-sensing circuit of the governor has the distinct advantage of having no moving mechanical parts which could be subject to wear or improper operation.

Having described one embodiment of my governor system, and several alternative circuit components thereof, it is believed obvious that other modifications and variations of my invention are possible in the light of the above teachings. Thus, other type of decoupling circuits 14 adapted for amplifying the AC component of the pressurized pulsations in the machine fluid and for converting a single-sided input signal to a push-pull signal, as well as other types of frequency-toanalog circuits 17 may be utilized in tachometer circuit 10. It is therefore to be understood that changes may be made in the particular illustrated embodiment of my invention which are within the full intended scope of the invention as defined by the appended claims.

I claim:

l. A fluidic speed governor adapted for controlling the speed of pneumatic and hydraulic machines by sensing the machine speed directly from pressure pulsations in the pressurized fluid supply, housing or exhaust of the machine comprising first fluidic circuit means having an input thereof in communication with the pressurized exhaust of a pneumatic or hydraulic machine for generating a pressurized fluid signal having a pressure magnitude proportional to the frequency of pressure pulsation in the pressurized fluid supply, housing or exhaust wherein the pulsation frequency is directly proportional to the actual machine speed,

the input to said first fluidic circuit means comprises a fitting connected to a sidewall of the exhaust muffler of the governed machine, and

tubing connected at a first end to said fitting, and at a second end to said first fluidic circuit means for transmining the pressure pulsations in the fluid exhaust line to said first fluidic circuit means, and

second fluidic circuit means in communication with an output of said first fluidic circuit means for generating a speed correcting pressurized fluid signal indicative of the deviation of the actual machine speed from a reference speed, said second fluidic circuit means provided with a second pressurized fluid input signal having a pressure magnitude proportional to the reference speed.

2. The fluidic speed governor set forth in claim 1 wherein said first fluidic circuit means includes a fluidic decoupling circuit for converting the pressure pulsations from a single-sided input signal to a push-pull pressurized fluid signal having amplitude of pressure variation substantially independent of the frequency of pressure pulsation in the single-sided input signal,

at least one proportional-type fluid amplifier in communication with said decoupling circuit for amplifying the output thereof, and a a fluidic frequency-to-analog converter circuit connected to the output of said at least one proportional fluid amplifier for converting the frequency of the pressure pulsations at the output thereof to a steady state pressure level signal having a pressure magnitude proportional to the frequency of pressure pulsations in the pressurized exhaust of the governed machine.

3. The fluidic speed governor set forth in claim 2 wherein the pressure magnitude of the steady state pressure signal is directly proportional to the frequency of pressure pulsations.

4. The fluidic speed governor set forth in claim 2 wherein the pressure magnitude of the steady state pressure signal is inversely proportional to the frequency of pressure pulsations.

5. The fluidic speed sensor set forth in claim 2 wherein said fluidic decoupling circuit comprises a first fluid passage comprising a control fluid inlet of said proportional-type fluid amplifier and provided with a first fluidic resistor, second fluid passage comprising a second and opposed control fluid inlet of said proportional-type fluid amplifier and provided with a second fluidic resistor and a fluidic reactive element in series circuit relationship therewith for determining a time delay circuit, the frequency corresponding to the time constant of the delay circuit being less than the minimum frequency of pressure pulsations in the pressurized exhaust of the governed machine,

said first and second passages have a common juncture at first ends thereof in communication with the pressurized exhaust of the governed machine.

6. The fluidic speed sensor set forth in claim 2 wherein said fluidic frequency-to-analog converter circuit comprises first fluid amplifier means connected to the output of said proportional-type fluid amplifier for developing a digitaltype pressurized fluid signal of repetition rate equal to the frequency of the pressure pulsations in the pressurized exhaust of the governed machine,

a single-receiver fluidic rectifier having a pair of opposed control fluid inlets in communication with the output of said first fluid amplifier means, and

at least one fluidic reactive element in communication with the control fluid inlets of said fluidic rectifier for developing a single-sided pressurized fluid signal having a pressure magnitude proportional to the frequency of the pressure pulsations in the pressurized exhaust of the governed machine.

7. A fluidic speed governor adapted for controlling the speed of pneumatic and hydraulic machines by sensing the machine speed directly from pressure pulsations generated by the moving parts of the machine in the pressurized fluid supply, housing and exhaust of the machine comprising a fluidic tachometer circuit having the input thereof in communication with the pressurized fluid supply, housing or exhaust of a pneumatic or hydraulic machine being controlled by said fluidic speed governor for generating a single-sided analog pressurized fluid signal having a pressure magnitude proportional to the frequency of pressure pulsation in the pressurized fluid supply, housing or exhaust wherein the pulsation frequency is directly proportional to the actual machine speed, the input to said tachometer circuit having no moving mechanical parts and including a fitting connected in the pressurized fluid supply, housing or exhaust of the governed machine, and

first tubing connected from said fitting to said tachometer circuit for transmitting the pressure pulsations thereto,

fluidic circuit means in communication with an output of tering said tachometer circuit while permitting the pressure pulsations therein to be transmitted to said tachometer circuit, said isolation circuit means comprising a source of clean pressurized fluid of pressure magnitude greater than the steady state pressure of the contaminated fluid,

a fluidic resistor, and

second tubing for connecting a first end of said resistor to said source of clean fluid and a second end to said first tubing,

the pressure of said source of clean fluid and the fluid flow resistance of said resistor having selected values to assure reverse fluid flow through said first tubing whereby the contaminated fluid is prevented from entering said tachometer circuit. 

1. A fluidic speed governor adapted for controlling the speed of pneumatic and hydraulic machines by sensing the machine speed directly from pressure pulsations in the pressurized fluid supply, housing or exhaust of the machine comprising first fluidic circuit means having an input thereof in communication with the pressurized exhaust of a pneumatic or hydraulic machine for generating a pressurized fluid signal having a pressure magnitude proportional to the frequency of pressure pulsation in the pressurized fluid supply, Housing or exhaust wherein the pulsation frequency is directly proportional to the actual machine speed, the input to said first fluidic circuit means comprises a fitting connected to a sidewall of the exhaust muffler of the governed machine, and tubing connected at a first end to said fitting, and at a second end to said first fluidic circuit means for transmitting the pressure pulsations in the fluid exhaust line to said first fluidic circuit means, and second fluidic circuit means in communication with an output of said first fluidic circuit means for generating a speed correcting pressurized fluid signal indicative of the deviation of the actual machine speed from a reference speed, said second fluidic circuit means provided with a second pressurized fluid input signal having a pressure magnitude proportional to the reference speed.
 2. The fluidic speed governor set forth in claim 1 wherein said first fluidic circuit means includes a fluidic decoupling circuit for converting the pressure pulsations from a single-sided input signal to a push-pull pressurized fluid signal having amplitude of pressure variation substantially independent of the frequency of pressure pulsation in the single-sided input signal, at least one proportional-type fluid amplifier in communication with said decoupling circuit for amplifying the output thereof, and a fluidic frequency-to-analog converter circuit connected to the output of said at least one proportional fluid amplifier for converting the frequency of the pressure pulsations at the output thereof to a steady state pressure level signal having a pressure magnitude proportional to the frequency of pressure pulsations in the pressurized exhaust of the governed machine.
 3. The fluidic speed governor set forth in claim 2 wherein the pressure magnitude of the steady state pressure signal is directly proportional to the frequency of pressure pulsations.
 4. The fluidic speed governor set forth in claim 2 wherein the pressure magnitude of the steady state pressure signal is inversely proportional to the frequency of pressure pulsations.
 5. The fluidic speed sensor set forth in claim 2 wherein said fluidic decoupling circuit comprises a first fluid passage comprising a control fluid inlet of said proportional-type fluid amplifier and provided with a first fluidic resistor, a second fluid passage comprising a second and opposed control fluid inlet of said proportional-type fluid amplifier and provided with a second fluidic resistor and a fluidic reactive element in series circuit relationship therewith for determining a time delay circuit, the frequency corresponding to the time constant of the delay circuit being less than the minimum frequency of pressure pulsations in the pressurized exhaust of the governed machine, said first and second passages have a common juncture at first ends thereof in communication with the pressurized exhaust of the governed machine.
 6. The fluidic speed sensor set forth in claim 2 wherein said fluidic frequency-to-analog converter circuit comprises first fluid amplifier means connected to the output of said proportional-type fluid amplifier for developing a digital-type pressurized fluid signal of repetition rate equal to the frequency of the pressure pulsations in the pressurized exhaust of the governed machine, a single-receiver fluidic rectifier having a pair of opposed control fluid inlets in communication with the output of said first fluid amplifier means, and at least one fluidic reactive element in communication with the control fluid inlets of said fluidic rectifier for developing a single-sided pressurized fluid signal having a pressure magnitude proportional to the frequency of the pressure pulsations in the pressurized exhaust of the governed machine.
 7. A fluidic speed governor adapted for controlling the speed of pneumatic and hydraulic machines by sensing the machine speed directly from pressure pulsations Generated by the moving parts of the machine in the pressurized fluid supply, housing and exhaust of the machine comprising a fluidic tachometer circuit having the input thereof in communication with the pressurized fluid supply, housing or exhaust of a pneumatic or hydraulic machine being controlled by said fluidic speed governor for generating a single-sided analog pressurized fluid signal having a pressure magnitude proportional to the frequency of pressure pulsation in the pressurized fluid supply, housing or exhaust wherein the pulsation frequency is directly proportional to the actual machine speed, the input to said tachometer circuit having no moving mechanical parts and including a fitting connected in the pressurized fluid supply, housing or exhaust of the governed machine, and first tubing connected from said fitting to said tachometer circuit for transmitting the pressure pulsations thereto, fluidic circuit means in communication with an output of said tachometer circuit for comparing the generated analog signal of said tachometer circuit to a single-sided analog pressurized fluid signal having a pressure magnitude directly proportional to a reference speed, for providing a signal proportional to the algebraic sum of the reference speed and the speed correction required for controlling the machine speed about the reference speed, and isolation circuit means connected at the input of said tachometer circuit for preventing contaminated fluid in the pressurized fluid supply, housing or exhaust from entering said tachometer circuit while permitting the pressure pulsations therein to be transmitted to said tachometer circuit, said isolation circuit means comprising a source of clean pressurized fluid of pressure magnitude greater than the steady state pressure of the contaminated fluid, a fluidic resistor, and second tubing for connecting a first end of said resistor to said source of clean fluid and a second end to said first tubing, the pressure of said source of clean fluid and the fluid flow resistance of said resistor having selected values to assure reverse fluid flow through said first tubing whereby the contaminated fluid is prevented from entering said tachometer circuit. 